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1.
Gas detection characteristics for NH3 gas have been studied for SnO2 mixed with ZrO2 and hydrophilic silica. Both an increase and a decrease in device conductivity can be obtained when the device is exposed to NH3 gas independently of the device temperature. This unique feature is exhibited when the device temperature is kept above 260°C. For a device mixed with 1 wt% hydrophilic silica, especially, a remarkable decrease in conductivity has been observed at 370°C device temperature. It is also found that this property can be utilized to make a highly selective NH3 gas detector, since the conductivity of SnO2-based devices usually increased for other reducing gases. Oscillation phenomena are also observed in devices mixed with 5 wt% hydrophilic silica at 370°C device temperature and 200 ppm NH3 concentration. The oscillation period varies from 4 to 20 min and the amplitude varies from 2 × 10?8 to 11 × 10?8 mho. 相似文献
2.
The CO response of Pd-doped tin oxide ceramics in both pellet and thick film versions is investigated. The porous thick film
samples exhibit more sensitive CO response than pellet ones. A linear relation between CO concentration and sample resistance
change is observed for samples doped with one wt.% PdCl2, while semi-logarithmic relations are obtained for samples doped with 2, 3 and 5 wt.% PdCl2. An optimum PdCl2 content of 2 wt.% yields the best response to CO gas. The existence of the optimum catalyst content is attributed to a synergistic
reaction. A possible mechanism for the CO sensing of tin oxide ceramics is explored. 相似文献
3.
The selective detection of CO gas by stannic oxide incorporated with ThO2(l − 10 wt%), in the presence of H2 and petroleum
gases such as C3H8 and iso-C4H2 has been studied. Materials mixed with 5 wt% ThO2 showed high selectivity to CO gas at a sample temperature of 200−250‡C. The effects of hydrophobic or hydrophilic silica
present in the samples on the detection sensitivity to CO gas have been investigated. From the results it is apparent that
the removal of the hy-droxyl radical from the surface of SnO2 enhances the sensitivity to CO gas. 相似文献
4.
SnO_2基CO气敏材料的制备与掺杂研究 总被引:4,自引:1,他引:3
以溶胶–凝胶法制备的SnO2纳米材料为基,采用Sb2O3掺杂改性,制备出CO气敏材料。用XRD分析了材料的结构、物相和颗粒度。通过同步TGA/DSC热重分析的方法分析了材料的稳定性。结果表明:掺入w(Sb2O3)为2%时,可以抑制晶粒度的长大,同时提高了材料的稳定性。工作温度在90~110℃变化时,气敏元件电阻值波动不大((R10R20) /R10= 12%)。R10和R20分别表示元件在空气中90℃和110℃时的阻值。 相似文献
5.
The temperature dependence of resistivities of gas sensors made of SnO2, Pd-doped SnO2, and ThO2-doped SnO2 with Pd has been investigated in air containing reducing gases such as CO, H2, and C3H8. The curves for ThO2-doped sensors were significantly influenced by the reducing gases as compared to the sensors without ThO2. From these results, it is found that in Pd-doped SnO2 sensors the dopant plays an important role in oxidizing the surface of SnO2 above 170°C, and that the addition of ThO2 to Pd-doped SnO2 enhances the effects of Pd by removing the adsorbed hydroxyl on SnO2. It is also apparent that the interactions between reducing gases in air and SnO2-based sensors depend upon the oxidizing rates of the surface of SnO2, as well as the amounts of the adsorbed hydroxyl on SnO2. 相似文献
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Wein-Duo Yang Yen-Hwei Chang Chia-Chia Huang Yu-Chung Chen 《Journal of Electronic Materials》2009,38(3):460-467
Highly sensitive CO gas sensors based on heterocontacts of ZnO:Al on La0.8Sr0.2Co0.5Ni0.5O3 (LSCNO) were fabricated successfully. La0.8Sr0.2Co0.5Ni0.5O3 thin films were coated on (100) silicon wafers by a sol-gel method including the Pechini process followed by a spin-coating
procedure. Then, ZnO:Al films prepared by radiofrequency (RF) magnetron sputtering at various oxygen partial pressures and
deposited on as-deposited La0.8Sr0.2Co0.5Ni0.5O3 films were investigated. The results revealed that the CO sensing ability of the film prepared with the ratio of O2/Ar = 5/5 (ratio of volume flow rate) was the worst, owing to the highest (002) plane orientation in the ZnO:Al film. In contrast,
the ZnO:Al film prepared with O2/Ar = 3/7 exhibited better CO sensitivity. Furthermore, all two-layer samples showed higher CO sensitivities than single-layer
samples. The CO sensitivity of ZnO:Al/La0.8Sr0.2Co0.5Ni0.5O3 thin film was 45% for 500 ppm CO at a sensing temperature of 200°C. 相似文献
9.
S. Jansat K. Pelzer J. García‐Antón R. Raucoules K. Philippot A. Maisonnat B. Chaudret Y. Guari A. Mehdi C. Reyé R. J. P. Corriu 《Advanced functional materials》2007,17(16):3339-3347
RuO2@SiO2 nanomaterials are prepared using hybrid mesostructured silica (EtO)2P(O)(CH2)3SiO1.5/x SiO2 (x = 9, 16) by anchoring the metal precursor [Ru(COD)(COT)] (COD is 1,3‐cyclooctadiene, COT is 1,3,5‐cyclooctatriene) inside the pores of the organized silica matrix through the phosphonate moieties. Following this task, the nanoparticles are fabricated by i) decomposing the metal precursor with hydrogen at room temperature in tetrahydrofuran to achieve ruthenium nanoparticles and ii) thermally treating the ruthenium particles in silica at 450 °C in air to fabricate RuO2. The materials containing Ru and RuO2 nanoparticles are characterized by elemental analysis, transmission electron microscopy (TEM), X‐ray diffraction (XRD), nitrogen sorption measurements, and 31P and 13C NMR. The obtained RuO2@SiO2 nanomaterials are evaluated as catalytic filters when deposited onto gas sensors for the preferential detection of propane in the multicomponent gas mixture propane/carbon monoxide/nitrogen dioxide. 相似文献
10.
Kunihiko Koike Shingo Ichimura Akira Kurokawa Ken Nakamura 《Journal of Electronic Materials》2002,31(2):108-112
We have investigated the characteristics of silicon oxidation by concentrated ozone gas through the comparison of the oxidation
by oxygen molecules. A sophisticated high-concentration ozone generator, which exploits the ozone/oxygen gas separation technique
with silica gel, has been developed for the study. The generator can continuously supply ozone-oxygen mixtures with ozone
concentrations up to 30 at.% at one atmospheric pressure. Ozone gas with a concentration of 25 at.% from the generator formed
SiO2 films as thick as 2 nm and 6 nm on Si for a 30 min. exposure at 200°C and 600°C, respectively. On the other hand, oxygen
gas by itself could form SiO2 films with only 1 nm and 3 nm thickness, respectively, at the same conditions. Moreover, in the oxide film formation at 600°C,
the oxide film growth by ozone was proceeded with an oxidation time in excess of 240 min., while it saturated within very
short time in the oxidation by oxygen. These phenomena verify the strong oxidation power of ozone. In addition, we confirmed
that the growth rate of the silicon oxide with ozone dramatically changed when the substrate temperature was over 500°C, and
this suggested the change of oxidation mechanism at this point. However, such a characteristic was not found in oxidation
with oxygen. 相似文献
11.
用纳米SnO2制作了旁热式气敏元件。用掺杂方法提高SnO2甲醛气敏元件的灵敏度,掺杂剂包括Pd,Sb,Ti,Zr,Cu,Ag,Mn等。在SnO2气敏元件中分别掺杂质量分数2%Pd和2%Zr对提高元件灵敏度有显著效果。未掺杂SnO2、掺杂质量分数2%Pd和2%Zr的气敏元件对体积分数为5×10-5甲醛的灵敏度分别为1.33,2.38,2.08,但是掺杂在改善元件对乙醇的选择性方面作用不大。分析了掺杂改善SnO2气敏元件灵敏度的原理,当SnO2表面吸附还原性气体时,吸附气体提供电子,使半导体表层的导电电子数增加,引起电导率增加、电阻下降。吸附气体浓度越高,电阻率变化越大,元件灵敏度越大。 相似文献
12.
Hui Huang Hua Gong Chee Lap Chow Jun Guo Timothy John White Man Siu Tse Ooi Kiang Tan 《Advanced functional materials》2011,21(14):2680-2686
Uniform SnO2 nanorod arrays have been deposited at low temperature by plasma‐enhanced chemical vapor deposition (PECVD). ZnO surface modification is used to improve the selectivity of the SnO2 nanorod sensor to H2 gas. The ZnO‐modified SnO2 nanorod sensor shows a normal n‐type response to 100 ppm CO, NH3, and CH4 reducing gas whereas it exhibits concentration‐dependent n–p–n transitions for its sensing response to H2 gas. This abnormal sensing behavior can be explained by the formation of n‐ZnO/p‐Zn‐O‐Sn/n‐SnO2 heterojunction structures. The gas sensors can be used in highly selective H2 sensing and this study also opens up a general approach for tailoring the selectivity of gas sensors by surface modification. 相似文献
13.
纳米氧化钨薄膜改性的大孔硅气敏传感器 总被引:2,自引:2,他引:0
通过双槽电化学腐蚀法在P型单晶硅表面制备了大孔硅。然后通过直流对靶反应磁控溅射法在大孔硅表面淀积了纳米氧化钨薄膜。使用场发射扫描电子显微镜(FESEM)观察大孔硅和氧化钨/大孔硅样品的形貌。分别使用X射线衍射(XRD)图谱和X射线光电子能谱(XPS)分析氧化钨晶体结构和钨的化合价。在室温下测试大孔硅和氧化钨/大孔硅气敏传感器的气敏特性。结果表明:氧化钨/大孔硅气敏传感器表现出了P型半导体气敏传感器的气敏特性。它对1ppm的二氧化氮显示了良好的恢复特性和重复性。氧化钨/大孔硅气敏传感器的长期稳定性要好于大孔硅气敏传感器。氧化钨的添加提高了大孔硅气敏传感器对二氧化氮的灵敏度。氧化钨/大孔硅气敏传感器对于二氧化氮的灵敏度要高于其对氨气和乙醇的灵敏度。通过淀积纳米氧化钨薄膜,改善了大孔硅对二氧化氮的选择性。 相似文献
14.
《Electron Devices, IEEE Transactions on》1979,26(3):247-249
A gas sensor of SnO2 -based materials has been made by thick-film technology utilizing hydrophobic silica as a binder. The technology can achieve a high productivity as well as a reduced humidity dependence and a sufficient mechanical strength of sensors. A thick-film sensor of SnO2 incorporated with ThO2 shows highly selective detection for CO gas, separated from H2 gas; i.e., sensitivity to CO is 42 times higher than to H2 at both gas concentrations of 50 ppm. An excellent humidity-independent sensitivity is also achieved. 相似文献
15.
MQS1型一氧化碳气敏元件 总被引:5,自引:0,他引:5
氧空位与材料的气敏特性有着密切的关系,气敏材料的电导率由氧空位的形成和氧化过程共同决定,氧空位浓度越大,气敏效应越明显。根据氧化锡的这一气敏机理,以99.99%的锡为原料,掺入合适的添加剂,制成了MQS1型一氧化碳气敏元件。它的灵敏度高、选择性好、响应恢复快、受温度和湿度的影响小。 相似文献
16.
Hae‐Ryong Kim Alexander Haensch Il‐Doo Kim Nicolae Barsan Udo Weimar Jong‐Heun Lee 《Advanced functional materials》2011,21(23):4456-4463
The humidity dependence of the gas‐sensing characteristics in SnO2‐based sensors, one of the greatest obstacles in gas‐sensor applications, is reduced to a negligible level by NiO doping. In a dry atmosphere, undoped hierarchical SnO2 nanostructures prepared by the self‐assembly of crystalline nanosheets show a high CO response and a rapid response speed. However, the gas response, response/recovery speeds, and resistance in air are deteriorated or changed significantly in a humid atmosphere. When hierarchical SnO2 nanostructures are doped with 0.64–1.27 wt% NiO, all of the gas‐sensing characteristics remain similar, even after changing the atmosphere from a dry to wet one. According to diffuse‐reflectance Fourier transform IR measurements, it is found that the most of the water‐driven species are predominantly absorbed not by the SnO2 but by the NiO, and thus the electrochemical interaction between the humidity and the SnO2 sensor surface is totally blocked. NiO‐doped hierarchical SnO2 sensors exhibit an exceptionally fast response speed (1.6 s), a fast recovery speed (2.8 s) and a superior gas response (Ra/Rg = 2.8 at 50 ppm CO (Ra: resistance in air, Rg: resistance in gas)) even in a 25% r.h. atmosphere. The doping of hierarchical SnO2 nanostructures with NiO is a very‐promising approach to reduce the dependence of the gas‐sensing characteristics on humidity without sacrificing the high gas response, the ultrafast response and the ultrafast recovery. 相似文献
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18.
High Performance Three‐Dimensional Chemical Sensor Platform Using Reduced Graphene Oxide Formed on High Aspect‐Ratio Micro‐Pillars
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Le Thai Duy Duck‐Jin Kim Tran Quang Trung Vinh Quang Dang Bo‐Yeong Kim Hock Key Moon Nae‐Eung Lee 《Advanced functional materials》2015,25(6):883-890
The sensing performance of chemical sensors can be achieved not only by modification or hybridization of sensing materials but also through new design in device geometry. The performance of a chemical sensing device can be enhenced from a simple three‐dimensional (3D) chemiresistor‐based gas sensor platform with an increased surface area by forming networked, self‐assembled reduced graphene oxide (R‐GO) nanosheets on 3D SU8 micro‐pillar arrays. The 3D R‐GO sensor is highly responsive to low concentration of ammonia (NH3) and nitrogen dioxide (NO2) diluted in dry air at room temperature. Compared to the two‐dimensional planar R‐GO sensor structure, as the result of the increase in sensing area and interaction cross‐section of R‐GO on the same device area, the 3D R‐GO gas sensors show improved sensing performance with faster response (about 2%/s exposure), higher sensitivity, and even a possibly lower limit of detection towards NH3 at room temperature. 相似文献
19.
Sensor nodes in ubiquitous sensor networks require autonomous replacement of deteriorated gas sensors with reserved sensors, which has led us to develop an encapsulation technique to avoid poisoning the reserved sensors and an autonomous activation technique to replace a deteriorated sensor with a reserved sensor. Encapsulations of In2O3 nanoparticles with poly(ethylene‐co‐vinyl alcohol) (EVOH) or polyvinylidene difluoride (PVDF) as gas barrier layers are reported. The EVOH or PVDF films are used for an encapsulation of In2O3 as a sensing material and are effective in blocking In2O3 from contacting formaldehyde (HCHO) gas. The activation process of In2O3 by removing the EVOH through heating is effective. However, the thermal decomposition of the PVDF affects the property of the In2O3 in terms of the gas reactivity. The response of the sensor to HCHO gas after removing the EVOH is 26%, which is not significantly different with the response of 28% in a reference sample that was not treated at all. We believe that the selection of gas barrier materials for the encapsulation and activation of In2O3 should be considered because of the ill effect the byproduct of thermal decomposition has on the sensing materials and other thermal properties of the barrier materials. 相似文献
20.
Shurong Wang Yingqiang Zhao Jing Huang Yan Wang Shihua Wu Shoumin Zhang Weiping Huang 《Solid-state electronics》2006,50(11-12):1728-1731
Tin dioxide nanocrystals were synthesized by a precipitation process and then used as the support for 2 wt.% gold/tin dioxide preparation via a deposition–precipitation method, followed by calcination at 200 °C. Thick films were fabricated from gold/tin dioxide powders, and the sensing behavior for carbon monoxide gas was investigated. The gold/tin dioxide was found to be efficient carbon monoxide gas-sensing materials under low operating temperature (83–210 °C). The Au/SnO2 sensor with SnO2 calcined at 300 °C exhibited better CO gas-sensing behavior than the SnO2 calcined at other temperatures. The experimental results indicated the potential use of Au doped SnO2 for CO gas sensing. 相似文献